German patent document DE 10 2004 056 120 A1 relates to a method for collision avoidance or collision consequence mitigation during a driving operation in which a motor vehicle approaches an obstacle, in particular a preceding vehicle; in one method, at least the relative speed between the motor vehicle and the obstacle is ascertained; a remaining time span until the latest onset of a collision-avoiding evasive maneuver, constituting an evasion time span, is ascertained; and a collision-avoiding or collision-consequence-mitigating action is taken as a function of the evasion time span that has been ascertained.
A variety of methods for trajectory planning are known in particular from robotics, on the basis of which methods a robot can be moved in collision-free fashion through a set of obstacles. These can refer to both a manipulator and a vehicle. The motion can occur in a two- or three-dimensional space.
Methods that take into account only stationary obstacles are known from practical use. Further methods are capable of also incorporating movable obstacles. The so-called “road maps” method connects all the vertices of the sensed obstacles to one another and thereby constructs a graph over all possible paths. Based on this graph, a route through an environment having obstacles can then be calculated. A procedure of this kind is discussed, for example, in US 2005/0192749 A1. There are also methods that subdivide the overall environment into collision-free and colliding cells, and connect a selection of collision-free cells into a collision-free route through existing obstacles. Such methods are, however, suitable only for stationary obstacles.
Methods based on virtual forces allocated to the obstacles also exist. If all the obstacles possess a repelling effect on the robot, and only the destination point has an attractive effect, it is possible to construct a potential field (similar to an electric field) through which a path through the obstacles can be calculated on the basis of the cumulative total force proportional to the gradient of the field. This principle is independent of whether the obstacles are or are not moving, since the path is determined only from the resulting total force of the field at the particular current point in time. Such methods can thus be used to the same extent for moving and non-moving obstacles. The robot guidance apparatus discussed in DE 42 07 001 A1 uses a resistance lattice having nodes, each of which represents an individual and discrete position within a travelable environment, and having connections between the nodes. Connections between nodes with an open circuit result in errors when the robot attempts to move along a travelable path, and can result in collisions with obstacles within the travelable environment.